METHOD FOR OPERATING A TWO-WHEELER

Abstract

A method for operating a two-wheeler. The two-wheeler includes a drive unit and a sensor system, the sensor system including a rotation rate sensor, an acceleration sensor, and a wheel speed sensor. The wheel speed sensor detects at least one measuring pulse per revolution of a wheel of the two-wheeler. The method includes: detecting three-dimensional rotation rates of the two-wheeler, detecting acceleration values of the two-wheeler, and estimating a motion state of the two-wheeler based on the detected rotation rates, the motion state including estimated values for estimated acceleration values and an estimated speed and an estimated distance covered, first correction of the estimated motion state based on the detected acceleration values, ascertaining an instantaneous steering angle of the two-wheeler based on the corrected estimated motion state, and actuating the drive unit and/or an antilocking system of the two-wheeler as a function of the ascertained instantaneous steering angle.

Claims

1-15. (canceled)

16. A method for operating a two-wheeler, the two-wheeler including a drive unit and a sensor system, the sensor system including a rotation rate sensor, an acceleration sensor, and a wheel speed sensor, the wheel speed sensor being configured to detect at least one measuring pulse per revolution of a wheel of the two-wheeler, the method comprising the following steps: detecting three-dimensional rotation rates of the two-wheeler using the rotation rate sensor; detecting acceleration values of the two-wheeler using the acceleration sensor; estimating a motion state of the two-wheeler based on the detected rotation rates, the motion state including estimated values for estimated acceleration values and for an estimated speed and for an estimated distance covered; first correcting of the estimated motion state based on the detected acceleration values; ascertaining an instantaneous steering angle of the two-wheeler based on the corrected estimated motion state; and actuating the drive unit and/or an antilocking system of the two-wheeler as a function of the ascertained instantaneous steering angle.

17. The method as recited in claim 16, wherein the actuation of the drive unit includes adapting a drive torque of the drive unit.

18. The method as recited in claim 17, wherein the drive torque of the drive unit is adapted based on a lookup table that includes a predefined drive torque profile as a function of the steering angle.

19. The method as recited in claim 18, wherein the drive torque profile is constant up to a predefined maximum steering angle, and for a steering angle greater than the predefined maximum steering angle, the drive torque profile is linearly dependent on the steering angle.

20. The method as recited in claim 19, wherein the predefined maximum steering angle is 10°.

21. The method as recited in claim 17, further comprising: ascertaining an instantaneous gradient of a roadway on which the two-wheeler is situated, wherein the drive torque of the drive unit additionally being adapted as a function of the gradient.

22. The method as recited in claim 16, wherein the actuation of the antilocking system includes: adapting a brake pressure in a braking system of the two-wheeler.

23. The method as recited in claim 22, wherein the adaptation of a brake pressure includes: controlling a pressure gradient of the brake pressure.

24. The method as recited in claim 23, wherein the controlling of the pressure gradient includes controlling a sensitivity factor and/or a maximum pressure of the pressure gradient.

25. The method as recited in claim 22, wherein the adaptation of brake pressure includes: controlling a tire slip during a braking operation of the two-wheeler.

26. The method as recited in claim 16, further comprising: ascertaining an instantaneous speed of the two-wheeler and/or a distance covered by the two-wheeler based on the corrected estimated motion state.

27. The method as recited in claim 16, further comprising: second correcting of the estimated motion state based on the measuring pulses that are detected using the wheel speed sensor.

28. The method as recited in claim 27, wherein the second correction is carried out based on the following equation:
y2=[x5,old+2πr] using a corrected value for a distance y2 covered by the two-wheeler, an old value for a distance x5,old covered by the two-wheeler, and a radius r of a wheel of the two-wheeler.

29. The method as recited in claim 16, wherein one or multiple of the following motion variables of the two-wheeler are ascertained based on the corrected estimated motion state: roll angle, pitch angle, longitudinal acceleration distance covered.

30. The method as recited in claim 16, wherein the first correction is carried out using a nonlinear Kalman filter.

31. The method as recited in claim 16, wherein the estimation of the motion state of the two-wheeler takes place using a state vector $x=\left[\begin{array}{c}x1\\ x2\\ x3\\ x4\\ x5\end{array}\right],$ where x1 is a roll angle, x2 is a pitch angle, x3 is a longitudinal acceleration, x4 is a longitudinal speed, and x5 is a covered distance, and using an input vector $u=\left[\begin{array}{c}u1\\ u2\\ u3\end{array}\right],$ where u1, u2, and u3 are the three-dimensional rotation rates, and based on the following system equation: $\stackrel{.}{x}-\left[\begin{array}{c}u1+\tan \left(x2\right)\sin \left(x1\right)u2+\tan \left(x2\right)\cos \left(x1\right)u3\\ \cos \left(x1\right)u2-\sin \left(x1\right)u3\\ 0\\ x3\\ x4\end{array}\right],$ the estimation of the motion state of the two-wheeler taking place based on a computation of an integral of the system equation {dot over (x)}, the estimation of the motion state of the two-wheeler also being carried out based on the following equations: $\mathrm{Rx}=\left[\begin{array}{ccc}1& 0& 0\\ 0& \cos \left(x1\right)& \sin \left(x1\right)\end{array}\right],$ $\mathrm{Ry}=\left[\begin{array}{ccc}\cos \left(x2\right)& 0& -s\mathrm{in}\left(x2\right)\\ 0& & 10\\ \sin \left(x2\right)& 0& \cos \left(x2\right)\end{array}\right],$ $\dot{\psi }=\frac{\left(u2\sin \left(x1\right)+u3\cos \left(x1\right)\right)}{\cos \left(x2\right)},$ $y1=R\mathrm{xRy}\left[\begin{array}{c}x3\\ -x4\dot{\psi }\\ g\end{array}\right],$ where {dot over (ψ)} is a yaw rate of the two-wheeler, and y1 are the estimated acceleration values of the two-wheeler.

32. A two-wheeler, in particular an electrically driven bicycle, comprising: a drive unit; an antilocking system; a sensor system that includes a rotation rate sensor, an acceleration sensor, and a wheel speed sensor; and a control device configured to controllably actuate the drive unit and the antilocking system, the control device configured to: detect three-dimensional rotation rates of the two-wheeler using the rotation rate sensor; detect acceleration values of the two-wheeler using the acceleration sensor; estimate a motion state of the two-wheeler based on the detected rotation rates, the motion state including estimated values for estimated acceleration values and for an estimated speed and for an estimated distance covered; first correction of the estimated motion state based on the detected acceleration values; ascertain an instantaneous steering angle of the two-wheeler based on the corrected estimated motion state; and actuate the drive unit and/or the antilocking system of the two-wheeler as a function of the ascertained instantaneous steering angle.

33. The two-wheeler as recited in claim 32, wherein the two-wheeler is an electrically driving bicycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention is described below based on exemplary embodiments in conjunction with the figures. In the figures, functionally equivalent components are in each case denoted by the same reference numerals.

[0044] FIG. 1 shows a simplified schematic view of a two-wheeler that includes a sensor system and a control device for carrying out a method according to one preferred exemplary embodiment of the present invention.

[0045] FIG. 2 shows an alternative view of the two-wheeler from FIG. 1 for illustrating a steering angle.

[0046] FIG. 3 shows an alternative view of the two-wheeler from FIG. 1 for illustrating an oblique position.

[0047] FIG. 4 shows a simplified schematic view of carrying out the method according to the preferred exemplary embodiment of the present invention.

[0048] FIG. 5 shows a simplified schematic view of a lookup table that is used in carrying out the method according to one preferred exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0049] FIG. 1 shows a simplified schematic view of a two-wheeler 1 that includes a sensor system 2 and a control device 20 for carrying out a method for ascertaining motion variables of two-wheeler 1 according to one preferred exemplary embodiment of the present invention.

[0050] Two-wheeler 1 is an electric bicycle, which in the area of a bottom bracket ball bearing includes a drive unit 12, with the aid of which a manually generated pedaling force from a rider of two-wheeler 1 may be motor-assisted. Drive unit 12 is supplied with electrical energy by an electrical energy store 14.

[0051] In addition, two-wheeler 1 includes an antilocking system 13 that is configured to actuate a hydraulic braking system 15 of two-wheeler 1. Antilocking system 13 is operable in an antilocking operation in which antilocking system 13 carries out a pressure modulation of a hydraulic brake pressure in hydraulic braking system 15 in order to prevent locking of wheel 11 during a braking maneuver. Antilocking system 13 is in particular connected to control device 20, and is actuatable with the aid of control device 20.

[0052] Control device 20 is situated at the handlebars of two-wheeler 1, and may be part of an onboard computer, for example.

[0053] Sensor system 2 includes multiple sensors. In detail, sensor system 2 includes a rotation rate sensor 21 and an acceleration sensor 22, both of which are integrated into control device 20.

[0054] Three-dimensional rotation rates of two-wheeler 1 are detected during travel with the aid of rotation rate sensor 21. A rotation rate is detected about each of axes x, y, z indicated in FIG. 1 (cf. also FIGS. 2 and 3).

[0055] The x axis is in parallel to a longitudinal axis L of two-wheeler 1 (cf. FIG. 2), which for straight-ahead travel of two-wheeler 1 is in parallel to a travel direction A. The z axis corresponds to a vertical axis H (cf. FIG. 3), which in particular is in parallel to a gravitational direction (not illustrated) of the earth's gravitational field. The y axis is perpendicular to the x axis and perpendicular to the z axis. The y axis may also be referred to as the pitch axis. In addition, the z axis may also be referred to as the yaw axis.

[0056] Acceleration values, preferably a total of three acceleration values, of two-wheeler 1 are detected along each of axes x, y, z with the aid of acceleration sensor 22.

[0057] In addition, sensor system 2 includes a single-pulse wheel speed sensor 23, designed as a rotation sensor, for detecting exactly one measuring pulse per revolution of a wheel 11 of two-wheeler 1. For this purpose, the wheel speed sensor is configured to detect the measuring pulse exactly once per revolution of wheel 11 each time it passes by a magnet 23a, which, for example, is fastened to a spoke of wheel 11. A rotational speed of wheel 11 may thus be ascertained, based on the measuring pulses that are detected with the aid of wheel speed sensor 23.

[0058] An instantaneous speed of two-wheeler 1, a distance covered, and an instantaneous steering angle δ are ascertained as motion variables of two-wheeler 1 with the aid of method 50.

[0059] Steering angle δ is illustrated in FIG. 2. FIG. 2 shows a view of two-wheeler 1 along the z axis. As is apparent in FIG. 2, steering angle δ corresponds to an angle between longitudinal axis L and front wheel 11. For straight-ahead travel, steering angle δ is equal to zero, and is correspondingly greater the smaller the radius of curvature of the curve that is negotiated by two-wheeler 1.

[0060] When negotiating a curve with two-wheeler 1, two-wheeler 1 is brought into an oblique position as illustrated in FIG. 3. FIG. 3 schematically shows an inclination angle β of two-wheeler 1. Inclination angle β is the angle by which two-wheeler 1 is inclined from vertical axis H.

[0061] Carrying out method 50 for operating two-wheeler 1 together with ascertaining the motion variables of two-wheeler 1 is described below with reference to FIG. 4.

[0062] In method 50, a detection 51 of the three-dimensional rotation rates of two-wheeler 1 initially takes place with the aid of rotation rate sensor 21. At the same time, a detection 52 of the acceleration values of two-wheeler 1 takes place with the aid of acceleration sensor 22. Based on the detected three-dimensional rotation rates, an estimation 53 of a motion state of two-wheeler 1 subsequently takes place.

[0063] The motion state of two-wheeler 1 includes estimated values for estimated acceleration values and for an estimated speed and also for an estimated distance covered. In detail, the estimation of the motion state takes place with the aid of a state vector that includes the following parameters: roll angle, pitch angle, longitudinal acceleration, longitudinal speed, and distance covered. In particular, the roll angle corresponds to inclination angle R, i.e., a deflection or a rotation of two-wheeler 1 about longitudinal axis L. The pitch angle preferably corresponds to a deflection or rotation of two-wheeler 1 about the y axis, i.e., transversely with respect to longitudinal axis L.

[0064] Based on the state vector and an input vector, the input vector including the three-dimensional rotation rates, a system equation is subsequently created which in particular represents a temporal change in the state vector.

[0065] Estimating 53 the motion state of two-wheeler 1 subsequently takes place by computing an integral of the system equation. The estimated motion variables of two-wheeler 1 are present in this way.

[0066] Correction steps 54, 55 of the motion state subsequently take place. A first correction 54 of the motion state initially takes place, based on the acceleration values that are actually detected with the aid of acceleration sensor 22.

[0067] A second correction 55 of the motion state additionally takes place each time that a measuring pulse of wheel speed sensor 23 is detected. In detail, the motion state is corrected based on the distance actually covered that is ascertained with the aid of wheel speed sensor 23. (Step 56.) Since the distance actually covered may be determined very accurately based on the geometric relationship of the measuring pulses across the circumference of wheel 11, a particularly accurate correction step of the motion state may be carried out with the aid of second correction 55.

[0068] Ascertaining 57 steering angle δ of two-wheeler 1 may subsequently take place based on the corrected motion state.

[0069] Method 50 may also be carried out in one modification (not illustrated) which additionally takes a standstill of two-wheeler 1 into account. Ascertaining a standstill of two-wheeler 1 additionally takes place based on the estimated motion state.

[0070] When a standstill of two-wheeler 1 has been ascertained, the state vector and the system equation may be reduced to the first two states. The situation may thus be avoided that the estimated motion variables drift as time passes, due to the absence of a measuring pulse, which may be used for second correction 55. As soon as it has been ascertained that two-wheeler 1 is once again moving, or as soon as a measuring pulse has once again been detected with the aid of wheel speed sensor 23, the state vector and the system equation are once more expanded to the original states prior to the reduction, so that an accurate determination of all motion variables is subsequently once again made possible.

[0071] As an alternative to a standstill of two-wheeler 1, an absence of a measuring pulse of wheel speed sensor 23 may also be used to reduce the state vector and the state equation to the first two states.

[0072] The once-corrected or twice-corrected motion state thus includes particularly accurate estimated values for the motion variables of two-wheeler 1. In particular, based on the corrected motion state, at any arbitrary point in time a desired motion variable, such as the speed, may thus be read off and for example used for further systems or methods of two-wheeler 1. In addition, by use of method 50 the motion variables of two-wheeler 1 may be precisely ascertained, even at very low speed, since method 50 is based in particular on the measured values of rotation rate sensor 21 and of acceleration sensor 22, which may provide precise and reliable measured values even at low speeds.

[0073] For two-wheeler 1, the ascertained motion variables, in particular steering angle δ, are/is used for actuating 58 drive unit 12 and antilocking system 13, as described below.

[0074] Actuating 58 drive unit 12 takes place in such a way that a drive torque generated by drive unit 12 is adapted as a function of ascertained instantaneous steering angle δ. Adapting the drive torque takes place based on a lookup table 30.

[0075] Lookup table 30 is illustrated in FIG. 5. Lookup table 30 is illustrated in the form of a diagram that represents drive torque 32 as a function of steering angle 31. A steering angle δ of 0° is present at axis 33.

[0076] Lookup table 30 includes a predefined drive torque profile 35 which defines the drive torque, to be set, as a function of ascertained steering angle δ. Drive torque profile 35 is symmetrical with respect to the 0° steering angle.

[0077] As is apparent in FIG. 5, drive torque profile 35 is constant within range C, it being possible to provide the maximum possible drive torque. Range C extends up to a maximum steering angle δ of 10°, in each case denoted by dashed lines 36.

[0078] For a steering angle δ greater than 10°, ranges B begin in each case, i.e., for steering to the left and to the right in both directions. A linear dependency of drive torque profile 35 on steering angle δ is present in ranges B. This means that with an increasing steering angle δ, the maximum drive torque proportionally decreases. If steering angle δ is greater than or equal to steering angle δ at points 37, which are situated at a steering angle δ of 45°, for example, the maximum possible drive torque is set to zero. This means that beginning with a steering angle δ of at least 45°, it is no longer possible for drive unit 12 to generate drive torque.

[0079] In addition, it may be provided that the drive torque of drive unit 12 is adapted as a function of an instantaneous gradient of a roadway on which two-wheeler 1 is situated. The gradient may, for example, be ascertained directly with the aid of sensor system 2 and/or based on the computed motion state of two-wheeler 1. When a predefined gradient is exceeded, a minimum drive torque of drive unit 12 preferably continues to be provided to allow a motor-assisted riding operation that is comfortable for the rider.

[0080] Furthermore, in method 50 for operating two-wheeler 1, actuating 58 antilocking system 13 takes place as a function of ascertained instantaneous steering angle δ. A pressure gradient of a brake pressure, which antilocking system 13 generates in hydraulic braking system 15 during an antilocking operation, is adapted as a function of ascertained steering angle δ. For an optimal braking behavior, it is particularly advantageous when a sensitivity factor and a maximum pressure of the pressure gradient are adapted during a pressure modulation in hydraulic braking system 15 that is carried out by antilocking system 13, based on ascertained instantaneous steering angle δ. In addition, control of a tire slip during braking of two-wheeler 1 may be carried out as a function of instantaneous steering angle δ.

[0081] For a particularly simple method of adapting the brake pressure for avoiding critical situations, for example in tight curves, the maximum brake pressure that is allowed in hydraulic braking system 15 may preferably be reduced with increasing steering angle δ. Excessive braking in tight curves, which could result in locking or slipping of wheel 11, may thus be avoided. As the result of using steering angle δ, which is estimated based on the motion state, for actuating 58 antilocking system 13, an antilocking operation that is optimized for negotiating curves with two-wheelers 1 may be provided using particularly simple and cost-effective means, since, for example, a complicated and costly sensor system, such as oblique position sensors or the like, may be dispensed with.